A New Facile and Rapid Synthesis of Polyamides and Polyimides by Microwave-Assisted Polycondensation

Abstract

A new facile method for the rapid synthesis of aliphatic polyamides and polyimides was developed by using a domestic microwave oven to facilitate the polycondensation of both ω-amino acids and nylon salts as well as of the salt monomers composed of aliphatic diamines and pyromellitic acid or its diethyl ester in the presence of a small amount of a polar organic medium. Suitable organic media for the polyamide synthesis were tetramethylene sulfone, amide-type solvents such as N-cyclohexyl-2-pyrrolidone (CHP) and 1,3-dimethyl-2-imidazolidone (DMI), and phenolic solvents like m-cresol and o-chlorophenol, and for the polyimide synthesis amide-type solvents such as N-methyl-2-pyrrolidone, CHP, and DMI. In the case of the polyamide synthesis, the polycondensation was almost complete within 5 min, producing a series of polyamides with inherent viscosities around 0.5 dL/g, whereas the polyimides having the viscosity values above 0.5 dL/g were obtained quite rapidly by the microwave-assisted polycondensation for only 2 min.Recently there has been growing interest in applying microwave energy to synthetic organic chemistry and synthetic polymer chemistry as well. In the latter field, microwave energy has been utilized for the radical polymerization of vinyl monomers such as 2-hydroxyethyl methacrylate (7), methyl methacrylate (2), and styrene (3) y and for the curing of polymers such as epoxy resins (4-10) and polyurethanes (77,72), as well as for the imidization of polyamic acids (13,14). Among them, much efforts have been directed toward the curing of epoxy resins from the practical viewpoint. In most cases, the high heat efficiency gave rise to remarkable rate enhancements and dramatic reduction of reaction times. However, there is no report so far except for our studies (15,16) on the synthesis of condensation polymers by using microwave energy. We have already reported the rapid synthesis of aromatic polyamides by microwave-assisted direct polycondensation of aromatic diamines and aromatic dicarboxylic acids with condensing agents(75j, and a preliminary study on the microwave-assisted rapid synthesis of polyamides from nylon salts (16). This article reviews the first successful rapid synthesis of aliphatic polyamides and polyimides by using a microwave oven to facilitate the polycondensation of both ω-amino acids and nylon salts, as well as of the salt monomers composed of aliphatic diamines and pyromellitic acid or its diethyl ester (16)(17)(18)(19).

Microwave‐Assisted Polymer Synthesis: State‐of‐the‐Art and Future Perspectives

“…Imai et al investigated the step-growth polymerization of aliphatic diamines H 2 N-(CH 2 ) x -NH 2 (x ¼ 6-12) with both pyromellitic acid and its diethyl ester (Scheme 2a). [21,26,27] Analogously to the synthesis of polyamides (Section 2.1. ), the reactions were performed in solution in a domestic microwave oven.…”

Environmental Remediation by an Integrated Microwave/UV-Illumination Method. 1. Microwave-Assisted Degradation of Rhodamine-B Dye in Aqueous TiO2 Dispersions

“…Microwave radiation has found its place in several domestic, industrial, and medical applications. Interesting reports have appeared on the application of microwave radiation in such technologies as (1) organic syntheses, polymerization ( , ) and dehydration ( − ) processes; (2) inorganic syntheses by ceramic calcination and solidification ( , ); (3) environmental waste treatment (); (4) safety and biological aspects ( − ); (5) analyses and extraction ( − ); and (6) food sterilization (). The microwave technique may also be useful in decomposing nondegradable materials from wastes.…”